Clinical Predictors of Dynamic Lower Extremity Stiffness During Running.

Abstract

Lower extremity stiffness describes the relative loading and kinematics of the entire lower extremity during ground contact. Previously injured subjects demonstrate altered lower extremity stiffness values. Clinical analysis of lower extremity stiffness is not currently feasible due to increased time and cost. To determine the clinically identifiable contributors to lower extremity stiffness. In this cross-sectional controlled laboratory study, 92 healthy runners completed a clinical screening involving passive assessment of hip, knee, and ankle range of motion, along with body anthropometrics. The range of motion was predominantly assessed in the sagittal and frontal planes. In the same session, runners completed an overground kinematic and kinetic running assessment at 3.35 m/s (±5%) to obtain lower extremity stiffness. Correlations between lower extremity stiffness and clinical variables were completed. Modifiable variables were included in an all-possible-linear regressions approach to determine a parsimonious model for predicting lower extremity stiffness. Clinically modifiable measures included in the regression model accounted for 48.4% of the variance of lower extremity stiffness during running. The variables that predicted greater stiffness included greater body mass, less ankle dorsiflexion range of motion with the knee flexed, less hip internal rotation range of motion, and less first-ray mobility. Reduced lower extremity range of motion and greater body mass are associated with greater lower extremity stiffness during running. These variables could be addressed clinically to potentially alter lower extremity stiffness and injury risk. J Orthop Sports Phys Ther 2019;49(2):98-104. Epub 27 Jul 2018. doi:10.2519/jospt.2019.7683.